README for the MASSES uv data for the pointing toward Per-emb-18 and Per-emb-21.

Visibility (uv) data is delivered for both the spectral lines and continuum.

The format for each spectral line uv data file in a MASSES dataverse is:
[targetname].[configuration].[linename].[tracknumber].uvfits

The format for the continuum uv data in a MASSES dataverse is: 
[targetname].cont[wavelength].[sideband].[tracknumber].uvfits

Continuum uv data are delivered for 1.3 mm and 850 um.
The delivered spectral lines at 1.3 mm are 12CO21, 13CO21, C18O21, and N2DP.
The delivered spectral lines at 850 um are 12CO32, HCOP, H13COP.
Table A3 in the full data release paper indicates which lines are detected for each pointing.

For Per-emb-18 and Per-emb-21, there is a single SUB track taken with the ASIC correlator: 141127
For Per-emb-18 and Per-emb-21, there are two EXT tracks.
Track 150915 was taken with the ASIC correlator.
Track 161024 was taken with the SWARM correlator.
No 850 um data was taken in the EXT configuration.

To import uvfits files into miriad, the "fits" task should be used. "op=uvin" and "options=varwt" must be specified. We show an example for CO(2-1) below:
fits in=Per18Per21.12CO21.141127.uvfits out=Per18Per21.12CO21.141127.miriad.uv op=uvin options=varwt

To import into casa, the task importuvfits should be used:
importuvfits(fitsfile="Per18Per21.12CO21.141127.uvfits",vis="Per18Per21.12CO21.141127.casa.uv")
Rest frequencies for each spectral line need to be specified in casa to show proper velocities.

This dataset also includes the full SWARM visibility data.
If the user is only interested in continuum or the spectral lines 12CO21, 13CO21, C18O21, or N2DP, these datafiles do NOT need to be used. The user should only use the data specified above.
SWARM visibility data has NOT had the continuum subtracted, like the data discussed above.
The dataset has EXT SWARM only.
The format for the EXT SWARM data is:
[targetname].SWARM.[wavelength].[chunk].[sideband].RECEIVERNUM.TRACK.uvfits
These EXT tracks had both SMA's 230 and 240 GHz receivers tuned to the same frequency. Both were combined when imaging.
Three SWARM chunks are available for each receiver of these EXT tracks.

These data can be imported in miriad or casa in the same way as above.
For these SWARM full visibility data, continuum subtraction should be done near the spectral line of interest.
Continuum subtraction can be done with miriad task 'uvlin' or with the casa task 'uvcontsub'.
